1. Filed of the Invention
This invention relates to a preparation for bioprecipitation of a soluble pigment in an aqueous solution and to a method for the treatment of the pigmented aqueous solution by the use of the preparation.
2. Description of the Prior Art
Substantially no effective method has been available to date for the removal of a water-soluble pigment from an aqueous solution. Barely a method which effects this removal by virtue of adsorption of the dissolved pigment on activated carbon has been resorted to heretofore. Another conventional method treats the pigmented aqueous solution with a bleaching agent not to remove the dissolved pigment but to whiten it. The former method requires to use the activated carbon in a large amount and entails a heavy cost and, therefore, fines utility only in special applications. The latter method only serves to decolorize apparently the pigmented solution and, therefore, suffers the principle of the soluble pigment, a coloring matter, to remain dissolved in the aqueous solution
The soluble pigment cannot be removed by any physical means like centrifugal separation. The adsorption of the dissolved pigment on the activated carbon or by the technique of ion column chromatography is about the only conceivable means. In the fields specializing in the prevention of environmental pullution, removal, decolorization, and deodorization of decomposed substances of carbon and other origins which are responsible for BOD (biochemical oxygen demand) constitute three major problems At present, the method for removal of substances causing unusual rise of BOD by the use of activated sludge, for example, has substantially reached the stage of perfection. The method of activated sludge, however, is next to totally incapable of decolorizing such dissolved substances.
In the circumstances, colored plant effluents have been disposed of by a method which comprises diluting such a plant effluent with a huge volume of water and discarding the diluted effluent into a nearby body of water and colored plant effluents and fermentation broths have been disposed of by a method which comprises concentrating such a colored waste water through evaporation of water at the expense of huge energy and either transporting the concentrate aboard by ship to be discarded in the open sea or consuming the concentrate by incineration. The method resorting to the disposal in the open sea is nothing more than an attempt to eliminate the residual waste in a manner invisible to the general public. When the environmental pollution is viewed on the global scale, this method merely serves the purpose of diffusing the waste thinly and widely over the entire surface of the earth. Thus, this method in effect is contributing to scattering the colored waste at random.
None of these conventional methods, therefore, is useful for efficient removal of soluble pigments from aqueous solutions.
The appreciation of this true status of affairs has led the inventors to form a theory that when the dissolved pigment is flocculated and precipitated in the aqueous solution and then the precipitate is separated through solid-liquid separation from the aqueous solution, the floccules of precipitated pigment can be collected and disposed of by incineration and that this disposal ought to prove highly advantageous from the economic point of view. With this theory in mind, the inventors have made various studies in search of a safe method for removing the soluble pigment without entailing the possibility of inducing secondary pollution of the environment. They have consequently found that the product of microorganic culture formerly developed by the inventors as a preparation for flocculating substances suspended in water (Japanese Patent Publication SHO No. 56(1981)-39633) manifests an outstanding effect in flocculating and precipitating such soluble pigments as have been unremovable from aqueous solutions by the conventional method like centrifugal separation. This invention has been perfected as the result.